Use Multi-Section Windings to Reduce Self-Capacitance

[David King]

Bagpipe,
Please understand that we're not to be taken too seriously here. We've run out of things to talk about re conventional pickups at least a decade ago but can't give up the bonhomie so we keep hoping to stumble into some esoteric corner of coilwinding lore to rediscover and pontificate upon with no intention of actually experimenting with it. It's a way for us to show off what we think we used know and to keep our narrow minds somewhat limber as we lumber off into our dotard-age. Talking "reason" at us won't change a thing.

I might point out that Snake-oil seems to sell to wanna-be musicians a whole lot better than EE-Facts.

[Leo_Gnardo]

The coily guitar cords were actually among the worst offenders IIRC. If they were popular it's because they killed off some treble and added crackly noises to the mix.

I can see the "charm" in using those awful coily cords. It's sort of like an editor who adds scratches, stains & jitter along with an umber tint to make video images seem antique. Similarly hiss, rumble & crackle are now digitally available to make a new recording sound like an old 45. There are times to use these things, and times to avoid them.

[Antigua]

You might not want to do anything that reduces the number of turns you can fit in the available space because you lose output, that is, unless there is something else to gain, and decreasing capacitance is not an important issue because the cable capacitance is much larger than the coil capacitance. Thus the contribution of the coil capacitance to the actual resonant frequency in use is not large.

If turns per available space becomes an issue, you just use a finer wire. If this design reduced capacitance from, say 130pF to 30pF, that 100pF savings is in the realm of becoming worthwhile.

However, the inductance with the split bobbin is interesting. Since the cores are short, all the flux from one coil does not pass through the other even if the permeability is high. It is not obvious to me whether the inductance changes with a split bobbin, or which way it changes if it does. Suppose it decreased with the split bobbin. Then you could add some more turns and get higher output for the same inductance.

Wouldn't the inductance just be reduced slightly due to the imperfect magnetic coupling? It should be less inductance than if there were no spacer in between, but higher than if you had two separate inductors in series.

[Antigua]

If you make a Jazzmaster type guitar pickup with six coils to reduce the pickup's capacitance, wouldn't this pickup be impossible to use 'normally' aka in a passive instrument's wiring environment? I think you would have to use a preamp with some strong toneshaping to sound anything like its passive counterpart.

The Jazzmaster analogy is just in terms of shape and not size. You would stack six miniature Jazzmaster coils, so that the resulting coil is still tall, like a more typical Fender pickup, but segmented into six sections that put a greater distance between the parts of the coil(s) where the difference in voltage is the greatest.

I
This is interesting. Would the cable capacitance of whatever the guitar cord is made of make a bigger difference to the sound than the pickup capacitance? I remember some people using coily guitar cords for this reason.

Ken

A 10' guitar cable usually features about 400pF-500pF capacitance, and a typical guitar pickup has around 100pF, so the cable capacitance is larger, but the pickup's capacitance is not so little as to not matter at all.

[rjb]

rjb: Sorry for the "shitty"

I take no offense to the "shitty".
I don't really take offense to the "paranoia". It just struck me as an odd word choice.

My point is, that i want to point on EE-Facts - rather than snake oil.

EE Fact 1: A long, curly, high-capacitance guitar cord will lower a pickup's resonant frequency enough to make an audible tone difference. Whether the resulting tone is good, bad, or indifferent is a matter of taste.

EE Fact 2: A long, curly, microphonic guitar cable with crappy right-angle connectors will crackle. Period.

-rb

EDIT: Wow, a lot of posts here since my last visit. That's what I get for taking a ten minute shower....

[Leo_Gnardo]

What about horizontal field arrangement? North left/South right

I think Gittler tried that on his "fishbone" guitars. Long spiral pickup windings paralleled the strings. One of these days I may have to deal with such a thing. A customer has one of 3 Gittler basses ever made, in pieces in his bureau drawer. It may fall to me to make its electronics work and I'm not looking forward to it. If the instrument can be restored, he may be able to flog it for beaucoup bucks.

I think the Gittler pickups were a subject of discussion on these pages many years ago. If I'm not mistook, the bottom line was, they were a terrible design - no wonder nobody carried on making anything like them. They got the Darwin Award for pickups iow.

[Antigua]

Now you are beginning to suggest multi-layer winding and such nonsense. Sorry - but...See:
Maybe you are able to reduce 130pF to 100pf or MAYBE to 82pF.

Based on the capacitance observed in a Jazzmaster pickup, I'd expect a pancaked coil design to possibly drop as low as 30pF.

[Bagpipe]

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[Bagpipe]

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[Bagpipe]

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[Antigua]

Anti-Gua:
reducing wire diameter results in higher DC_Resistance if you want to achieve same inductance. OR: You use a stronger magnet.

The series resistance is fairly trivial. Even another 10k series resistance isn't going to decrease the output by any significant amount.

Inductance wouldn't be decreased AT ALL. At least not in common measurement ranges. The difference is SO SMALL, that it plays no role. It gets swamped practically with differing magnet-specs, string/pole distance and so on. I can assure you, that you wouldn't notice the change from single to split-bobbin AT ALL!

You wouldn't even notice the loss due to smaller wire Diameter.

Why is it so?

Because a pickup is so damn NON-IDEAL in every way. Ever considered the amount of leakage flux? Especially in connection with closed HumBuggers?

A guitar pickup has rather tight winding-to-winding magnetic coupling, even if the core is so open as to be nearly air, which is why the inductance is as high as it is despite the imperfect core. So if the windings were broken into two halves, I'd expect some drop, but maybe it would only be a matter of millihenries.

[Antigua]

And STILL:

30pf Or 130pF plays STILL no role. Why? You tell me...

http://music-electronics-forum.com/t46404-5/#post495799

30pf Or 130pF plays STILL no role. Why? You tell me...

Two reasons: 1) that's like 2.5 feet less guitar cable with the volume on 10, 2) as you turn the volume down and the capacitance of the cable is separated from that of the guitar pickup, the pickup's lower intrinsic capacitance plays a greater role, and so a lower C works to preserve top end as the volume is rolled off.

[Mike Sulzer]

" because you lose output"
Do you? I mean: Significantly?

I hope it is clear, that you decrease Copper-Loss at the same time, you unwind your coil.

Inductance falls. This is all. And with this, a lot of side-effects (including losing a LITTLE output) come....

P.S. Thanks a lot (*NOT*) for your reply to my request, Mr. Sulzer. How friendly of you...

That made sure that I will not be replying to the request you made in a private message.

I think the issue is that the dividers take up space.

[Bagpipe]

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[Bagpipe]

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